NASA Technical Reports Server (NTRS) 20020076153: Intelligent Fasteners

Transportation

Intelligent

n f you are facing rhat oft-quoted engineering
truism, chat a system is only as good as its
weakest link* consider the worlds first, high-
tempera lure-resistant, “intelligent*’ fastener.

A product of Ultrafast, Inc. of Malvern, Pennsylva-
nia, this fastening technology was originally developed
under a Small Business Innovation Research (SBIR)
contract managed by Marshall Space Flight Center. The
NASA partnership was born by a need for critical-
fastening appraisal and validation of spacecraft segments
that are coupled together in space. In-orbit assembly
requires both lightweight wrenches for enhanced robot'
arm mobility as well as remote fastener-load inspection
capability.

The space solution yielded an innovation that is
likely to revolutionize manufacturing assembly, particu-
larly in the automobile building industry.

Ultrafasts “intelligent bolt” utilizes a piezoelectric
rh in-film deposited directly on one end of the fastener.
When electrically excited by an Uhrafast tool, tensile
loads can be accurately controlled during the bolt
tightening process. Insufficient boh preload is usually
the root cause of joint failure resulting from joint
separation, bolt loosening or fatigue.

In effectj a bolt topped by the thin-film
technology — at a cost of just pennies per fastener-
functions as a transducer for measurement and recording
of bolt tensile load. The coating itself is less than 0.001
inch thick and is durable, deposited on the fastener by
sputtering. This is a vacuum process that has long found
practical application in everything from integrated
circuits to reflective coatings on glass or decorative
coatings on plastic. Moreover, the coating can he applied
ro all forms of existing fasteners without changing the
basic design or metallurgy of the item undergoing the
process.

Ultrasonic measurements of a fastener are possible
by using piezoelectric thin films, in both longitudinal
and transverse directions, heretofore impractical in
typical fasteners. Ultra fast technology uses the relation-
ship between the speed of ultrasonic waves in a material
and the stress applied to the material as its basis for
computing load measurements. The idea is that the
“time- of- flight” of an ultrasonic signal traveling in a
fastener will increase as the load on the fastener is
increased,

Ultrafasfs intelligent -bolt technology deletes the
self-defeating procedure of having to untighten the
fastener, and thus upset the joint, during inspection and
maintenance. Even the smallest fastener can be turned
into latent sources of information in numerous applica-
tions.

Fasteners

For the automotive industry, the advantages of
applying the Uhrafast system are distinct. Safety-critical
components like powertrains, steering systems and
brakes can achieve higher reliability while minimizing
service costs and other impacts from joint failure. Use of
high speed impact or impulse wrenches to improve joint
integrity and inspection can lower costs in automotive
body manufacturing by reducing joint assembly times.

Practical use of ultrasonic thin-film fasteners go
beyond the realm of automobile, aircraft, and space
applications. For instance, from computer disk drive
assemblies to forklifts. In the nuclear field, from small
flanges to large pressure vessels. For chemical processing,
critical -fastening applications include offshore platforms
to pipes. In construction, the appeal of Ultrafasds
innovation can be applied to buildings and bridges.

Uhrafast expects sales to exceed $ 100 million in a
few years. Ultrafast has licensed two major European
cool companies to supply power tools for automotive
assembly and is establishing worldwide fastener coating
services through its Ultracoar subsidiaries.

Uhrafast V f *in tell igett t” fasten e ) ‘S are expected to be a boon to
automobile man ufaettt rers t assuring that more precise loads are
applied during bolt tightening.

Commercial Ben etits — Spinoffs